The present invention relates to a process for the preparation of hydrogenosilanes from disilanes.
Various processes for the preparation of hydrogenosilanes from disilanes have already been described. Thus, in Synthesis of Organosilicon Monomers (English translation published in 1964 by HEYWOOD & COMPANY, LTD), paragraph 5 of chapter XV, various methods are cited, for example, methods which use hydrochloric acid whereby the reaction is accelerated by using certain catalysts, such as the chlorides of copper, antimony and mercury, and methods which use bases such as ammonia, trimethylamine and diethylamine. This publication also mentions a method of treating residues from the direct synthesis of chlorosilanes, which allows to obtain methyl-hydrogeno-dichlorosilane by using hydrochloric acid and certain catalysts (alumina and silicic acid). Methods for treating the residues of the direct synthesis, which consists of mixtures of compounds, including, amongst others, disilanes, are described, for example, in the French Pat. No. 1,093,399, No. 2,085,143 and No. 2,163,579. However, it should be noted that the French Pat. No. 1,093,399 is essentially concerned with the scission of Si-Si, Si-O-Si or Si-C-Si bonds and the technique which is described in this patent (using hydrochloric acid and heating between 200 and 900.degree. C) yields only a very small amount of hydrogenosilane. Likewise, in the French Pat. No. 2,163,579, according to which a disilane is reacted with a halide in the presence of platinum, or palladium, or a phosphine complex of platinum, palladium or nickel, the intention is essentially to prepare halogenosilanes containing hydrocarbon substituents and not hydrogenosilanes.
French Pat. No. 2,085,143 aims more precisely at the preparation of hydrogenochlorosilanes. According to this patent, scission of the disilanes and their hydrogenation is carried out at the same time. This operation comprises bringing the disilane into contact with gaseous hydrogen under pressure, at a temperature of between 25.degree. and 250.degree. C in the presence of at least 1%, by weight, relative to the disilane, of a transition metal catalyst. According to this document, this catalyst can be palladium, ruthenium, rhodium or an organophosphine complex of a transition metal, especially palladium, platinum or nickel. This process is of interest if hexamethyldisilane or monochlorinated or dichlorinated derivatives are used as starting disilane. When trichlorinated or tetrachlorinated derivatives are concerned, the technique described in the patent usually requires conditions which make industrial exploitation difficult.